Photo-electric cell



' A. H. COMPTON PHOTO ELECTRIC CELL Filed March 1, 1921 "Patented Dec.29, 1925.

UNITED STATES PATENT OFFICE.

ARTHUR H. COMPTON, OF ST. LOUIS MISSOURI,.ASSIGNOR TO WESTINGHOUSE LA'MPCOMPANY, A GORI ORA'IION OF PENNSYLVANIA.

PHOTO-ELECTRIC CELL.

Application filed March 1, 1921. Serial No. 448,944.

My invention relatesto photoelectric cells and has more particularrelation to the pro duction of an alkali-metal cell in which thelight-sensitive alkali metal, for example,

potassium, is evenly distributed over, and in intimate contact with, alimited portion of an evacuated-cell envelope.

In order to secure this even distribution and intimate contact, it isdesirable to em ploy a deposition method, for example, the condensationof a light-sensitive material in gaseous or vapor form. In alkali-metalcells it is essential, however, that a portion of the dielectricenvelope between the electrodes shall be preserved free from metaldeposit. The limitation of the de osit to a portion of the cell envelo eand tile preservation of some portion 0 the cell envelope between theelectrodes free from deposited metal is the primary object of thisinvention.

One way in which this object may be obtained is by providing astructure, as shown in the accompanying drawing, having an auxiliarytube, preferably located around the leading-in conductor to one of theelectrodes and communicating with the cell envelope proper. This tube isprovided with an lrregular or sinuous channel at some portion thereof,the sinuosities of the channel providing a partial barrier to interceptthe volatilized light-res onsive material and thereby preventing it rombeing deposited on-some portion thereof. The result is that some portion,of the cell envelope along which current might flow between theelectrodes, is preserved free from deposited light-responsive material,while the remainder of the envelope is coated with such materialadhering to the cell envelope.

In order to illustrate my invention I have s ho wn one embodimentthereof in the accompanying drawing in which a longituic, is shown.

An evacuated electrode-containing chamber A is preferably provided witha laterall'y-extending distillin tube or reservoir B adapted to containght-responsive mate- ,partly, diagrammatrial, at least in sufficientquantity to adequately coat the desired portion of the wall or envelopeof the chamber.

An electrode C is located on the inner face of the wall or envelope ofchamber A and at any convenient point thereof. The electrode C may be,and preferably is, connected to a lead wire sealed in the wall of thechamber ,A in the usual manner. A double-wall side tube D is arranged tocommunicate with the chamber A and is referably formed integrallytherewith. gonveniently, the double-wall side tube D is located on theside of the chamber A opposite to the tube B, to preserve the symmetryof the arrangement. The tube D com rises an outer shell E and areentrant fold forming a crater-like tube the shell E and the fold Fbeing spaced from each other and each provided with correspondingbulbous or swollen portions J and K, respectively. The space between theouter shell E and the reentrant fold F forms an annular pocket whichcommunicates with the chamber A through the restricted neck L. Thebulbous portions J and K provide sinuosities in the pocket, whichconstitute a barrier and thereby cause a condensation of the volatilizedlight-responsive material when it comes into contact with saidsinuosities. 1

A second electrode M is located within the chamber A to receive itsenergy through a suitable lead wire which may, and refer ably does,extend through the fol F .of the side tube D, being sealed therein inthe usual manner.

In preparing the cell for use, the alkali metal, specifically potassium,contained in the chamber B,'is volatilized, the volatile material assinginto chamber A and being condensed on the walls thereof in asubstantially even layer having intimate contact with the wall ofchamber A. The How of the volatilized material into the annularirregular pocket formed in the side tube D is substantially prevented bythe condensation of the material at'the mouth of the shadow thereof.

evacuated envelope consisting a comparatively wide zone extending sub'stantially from the equator of the enlarge- .ment K to the restrictedortion L of the envelope.

It should be urther noted that there are two distinct shadow zones orportions protected from the vaporized material emanating from thechamber B,- namely that portion of the outer wall of the shell E in theshadow of the restriction L and that portion of the reentrant foldforming the rear side of the enlargementK and in the Evidently, if asingle bulbous region is insuiiicient to adequately intercept thevolatilized material and prevent it from passing into the tube D, aplurality of such bulbous regions may be used.

' Although I have found potassium and sodium to be particularly adaptedfor use in practicing my invention, rubidium and caesium may also proveto be suitable lightresponsive materials which may be screened in thesame manner as potassium. Also, it

maybe found desirable to limit the deposited area in cells employinglight-sensitive materials other than those mentioned. Hence, when Ispecifya light-sensitive material, I mean to include such materials,other than potassium, as may be found suitable.

What is claimed is:

l. A photo-electric cell comprising an envelope consisting of a mainchamber andan auxiliary chamber connected by a restricted neck, saidauxiliary chamber having a curved passage-forming a plurality of shad-OW zones, an electrode extending through the wall of the auxiliarychamber and the neck into the main chamber and another electrodeextending through the wall of the main chamber, light-sensitive materialdeposited on the wall of the main chamber, connected with the secondelectrode and ins'ulated from the first electrode by said shadow zones,2. A photo-electric cell comprising an envelope consisting of a mainchamber and an auxiliary chamber of non-uniform cross sec-- tion andconnected ,to the main chamber by a restricted neck, an electrodeextending through the wall of the auxiliary chamber and the neck intothe main chamber, the interior of the wall of the main chambersubstantially uniformly coated with a lightsensitive material insulatedfrom the electrode and electrically connected to a-leading-in wire.extending through the wall of the main chamber.

3. A photo-electric cell comprising an of a main chamber interiorlycoated wit alkali metal and an auxiliary annular chamber with a chamberand the. restricted portion into the main chamber and a cathodeconductor extending through the wall ofthe main cham-' ber'and connectedto the deposit of alkali metal on the interior of said wall, butinsulated from the leading-in conductor of the anode by said sinuouschannel. a

4. A photo-electric cell comprising an envelope consisting of a mainchamber and an auxiliary annular chamber having a reversely curvedchannel and connected to the ,main chamber by a restricted portion, anelectrode in the main chamber and connected to a leading-in conductorextending through the restricted portion and the wall of the auxiliarychamber, another electrode extending through the wall of the mainchamber'and means for introducing alkali metal into the main chamber asa substantially uniform film on the wall thereof, without depositing iton the wall of the'auxiliary' chamber to a sufficient extent to form ashort-circuiting path between the electrodes.

5. An envelope for an electric device comprising a'main chamber-and anannular aux iliary chamber having a reversely curved channel andconnected to the main chamber by a restricted portion and means forintroducing an alkali metal into the main chamber, said alkali metalbeing maintained out of contact with a substantial portion of said iauxiliary chamber. by said reversely curved channel and said restrictedportion.

6. An envelope for a photo-electric cell comprising a main chamber, anannular auxiliary chamber having a curved channel and connected to themain chamber by a restricted portion and a tube containing an alkalimetal connected to the main-chamber whereby a deposit of the alkalimetal may be formed on the inner wall of the main 7. A photo-electriccell comprising an.

envelope having a main chamber, a film electrode on the inner surfacethereof an auxiliary chamber associated therewith having a reentr'antstem portion, asecond electrode carried by said stem portion andextending into the main chamber, the outer wall of said auxiliarychamber and said reentrant stem defining a reversely curved annularpassage havinga plurality of zones free from said filmelectrode materialwhereby I said electrodes are insulated from eac other. I V

In testimony whereof, I have hereunto subscribed my name this 24th dayofFebruary, 1921., 1 i

ARTHUR H. eo PTon.

